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In subclause 4.45.4 of the description of the
od utilityØs file operand
(P371, L7342-7346), it says:
"file A pathname of a file to be read. If no file
operands are specified, the
standard input shall be used. The
results are unspecified it the first character of
file is a plus sign (+) or the
first character of the first file
operand is numeric, unless at least one of the
-A, -j, -N, or -t options is
specified."
Although the rationale doesnØt say this, it
seems obvious that the intent of
the last sentence in this
description was to allow implementations to
provide an obsolescent
synopsis form, corresponding to
historic practice, along the lines of:
od [-bcCDdFfOoSsvXx] [filename]
[[+]offset[.][b]]

Unfortunately, one common command form:
od -c file 10.
is not allowed because the offset operand is
identified by a numeric as the
first character of the "second"
file operand. Although the wording in the
standard would allow the
command:
od -c 10.
to treat 10 as a decimal offset (rather than as
a filename), historic practice
(in both System V and BSD
implementations) required this to be specified
as:
od -c +10.
To allow implementations to actually provide
the historic forms as
extensions, the phrase "first character of
the first file operand" on P371, L7344-7345
should have been "first
character of the second file
operand".
Was this wording intended to prevent
implementations from supporting
historic behavior, or was this an
editorial mistake?

Interpretation Response
The standard states the behavior for the file
operand of the od cmd and
conforming implementations must
conform to this. However, concerns have
been raised about this which are
being referred to the sponsor.